Disease Causes and Transmission

Disease Causes

Infectious Diseases

Influenza virus droplet inflammation of respiratory tract, fever, headache
Cold sores (Herpes simplex) virus direct contact blisters on lips and gums
Genital Herpes virus sexual contact burning sensation on genitals, blisters and painful ulcers, may cause cervical cancer in women
Tetanus bacterium deep wound contaminated with infected soil muscle paralysis, death in severe cases
Cholera bacterium having food or drink contaminated with infected faeces severe diarrhoea, high fever, some intestinal damage
Botulism (food poisoning) bacterium eating food containing a bacterial toxin muscle paralysis, death in some cases
Tinea (Athlete's Foot) fungus contact with contaminated wet floors towels or shoes cracks in the skin between toes, itching
Malaria protozoan vector of Anopheles mosquito muscular pains, chills, fever, sweating, death in some cases
Tapeworm infection tapeworm having food or drink contaminated with infected faeces malnutrition, weight loss

Non-Infectious Diseases

Did You Know...? In 1770, Captain Cook was the first ship's captain to have an entire ship's crew free of scurvy. He fed his sailors pickled cabbage containing Vitamin C, and if they refused to eat it, they were flogged.

Defence and the Immune System

Lines of Defence

Non-Specific Response Mechanisms

Specific Defence Mechanisms

Specific Defence

Humoral Immunity

B-lymphocytes (B cells) produce specific antibodies that can bind to 2 antigen molecules. Most antibodies are large globular proteins called immunoglobulins that are released into blood plasma. Antibodies also coat foreign particles so that they are recognised and engulfed by macrophages.

B cells are formed in bone marrow and the spleen, and when they become active, they form 2 types of daughter cells - plasma cells (which make antibodies) and memory cells (which remain in lymphatic tissue for some time and provide a long-term immunity after a person has encountered a disease).

Cell-Mediated Immunity

T-lymphocytes (T cells) are produced in the thymus gland and act against eukaryotic cells such as infected or cancerous cells.

There are 2 types of T cells - Cytotoxic T cells (directly kill infected or foreign cells) and Helper T cells (assist in regulating the B cells and the cytotoxic T cells).

Rejection of Transplanted Organs

Preventing and Treating Disease

Preventing Disease



Monoclonal Antibodies


Did You Know That...? Leonardo da Vinci was famous for painting the 'Mona Lisa', inventing the first helicopter and various weapons of warfare. Also as far back as 1500, he proposed that bombs containing a liquid extracted from the saliva of a mad pig or dog should be dropped on the enemy. That was the first example of biological warfare.